Valve Assembly

ABSTRACT

The invention relates to a valve assembly that can be provided of a length to meet conventional fitting dimensions and requirements. The valve assembly includes a valve body housing, at least first and second valve balls. Between the first and second valve balls are provided first and second valve seats. The valve seats are biased towards their respective valve balls by common biasing means. The valve seats, that lie between the valve balls, are typically provided as part of a common valve seat assembly that includes the biasing means.

The invention to which this application relates is to a valve assembly.Particularly, although not necessarily exclusively the invention relatesto an improvement to the type of valve known as a double block and bleedvalve in which typically three independent valve units are providedwithin a valve body.

The provision of double block and bleed valves is well known in theindustry and the applicant has several granted patents in this field.One common problem, which is experienced with this form of valve, is therequirement to fit the valve assembly into the space, which is availablebetween adjacent pipe flanges. For larger diameter pipelines inparticular the length of the conventional double block and bleed valveassembly can be greater than the ANSI B16.10 specified space. This meansthat if, for example, the conventional double block and bleed valve isbeing used to replace a single valve in an existing pipeline, the spaceavailable is too small. This therefore means that additional works arerequired to be performed on the pipeline, which can lead to additionaltime and expense being incurred.

A further problem is that the conventional double block and bleed valveassembly includes a significant number of components, which add to thecomplexity of the assembly process and the time for assembly.

The aim of the present invention is therefore to provide a valveassembly which can more readily be provided of a length to meetconventional fitting requirements. A further aim is to provide a valveassembly, which can be more easily assembled whilst at the same timeproviding the required operating performance.

In a first aspect of the invention there is provided a valve assembly,said valve assembly including a valve body housing, first and secondvalve balls and between said first and second valve balls are providedfirst and second valve seats wherein said valve seats are biased towardstheir respective valve balls by common biasing means.

Typically said biasing means are springs and more typically coilsprings. Typically said biasing means are positioned to lie between saidfirst and second seats with a first end of said biasing means acting onthe first seat and the opposing end of said biasing means acting on thesecond seat. In one embodiment, when the fluid flows through the valvein a first direction, the biasing means acts on one of the first orsecond seats to move the same towards the first or second valve ballrespectively, and when the fluid flows through the valve in the opposingdirection the same biasing means act on the other of the first or secondseats to move the seat towards the other of the first or second valveballs.

In one embodiment the first and second seats and the biasing means areprovided as a seat assembly which is located within the valve assembly.

The valve seats are typically provided to seal against the valve balland typically the strength of the biasing means, and/or the number ofthe same which are provided are selected with respect to the fluidpassing through the valve, the size of the valve passage along which thefluid flows and/or the pressure of the fluid. When a number of biasingmeans are provided the same are typically spaced around thecircumference of the passage of the valve.

Typically the fluid acts in conjunction with the biasing means to exertthe movement force on said first or second seat depending on thedirection of flow of the fluid.

In one embodiment the valve body is formed from two parts, the interfaceof which is located at, or close to, the location of the seats andbiasing means. Alternatively, the valve body is formed of one part andthe seats and biasing means are introduced into position from an end ofthe valve body.

Typically the valve assembly includes a passage from a first end to asecond end and the first and second valve units are provided spacedalong the passage, each valve unit provided to allow the selectiveclosing and opening of the passage.

In one embodiment there is provided a vent located intermediate thefirst and second valve units. In one embodiment the vent passage isformed around the circumference of the seat assemblies.

By providing biasing means which act on both seats so the overall lengthof the valve assembly can be significantly reduced and, importantly, canbe reduced sufficiently so that the same is at or less than the requiredANSI B16:10 length for the particular pipe diameter. Also, as the lengthof the valve body can be reduced so material savings can be made whichcan lead to significant savings in weight and material costs incurred.

In a further aspect of the invention there is provided a double blockand bleed valve assembly, said assembly including a first ball valveunit and a second ball valve unit spaced apart in a fluid passagethrough the valve assembly and wherein intermediate said first andsecond valve balls there is provided a seat assembly including a firstseat and a second seat and biasing means to exert a biasing force on thefirst and second seats in opposing directions.

Typically the same biasing means exerts the biasing force on both thefirst and second seats and is retained in position between the same.

Typically the biasing force is used to move each seat to seal on thevalve ball of the respective first or second valve unit.

In one embodiment the biasing means are spaced around the circumferenceof the seats so as to exert a constant movement force around the seat.

Specific embodiments of the invention will now be described; wherein;

FIGS. 1 illustrates a conventional double block and bleed valvearrangement in section along the longitudinal centre axis;

FIGS. 2-3 illustrate a valve assembly in accordance with two embodimentsof the invention in section along the longitudinal centre axis; and

FIG. 4 illustrates a detailed view of the seat arrangement in accordancewith the invention.

Referring firstly to FIG. 1 there is illustrated a conventional form ofa double block and bleed valve assembly 2. Said assembly comprises abody 4, which has a passage running between ends 8, 10. The housingcontains two ball valve units 12, 14 each of which include a valve ball16 with respective seats 18, 20, 18′, 20′ on either side. The seats 18,20 are biased onto the respective ball 16 by biasing means in the formof springs 22 which are mounted on the valve body at one end and theother end acts on the seat to force the same towards the ball. Typicallythe springs are provided in sufficient number and of a size to suit thesize of valve assembly to ensure that sufficient force is applied to theseat onto the ball so as to allow a seal to be created.

The seats 18′20′ lie intermediate the valve balls 16 and conventionally,as shown, in order to allow the seats and springs to operate correctly aland portion 24 is provided in the valve body. The provision of the landportion causes the length of the valve assembly, at least for certainsizes, to be greater than the ANSI B16:10 standard length which causesproblems in terms of expense and time of installation.

FIGS. 2-4 illustrate two embodiments of a valve assembly 102 inaccordance with the invention. The parts of the valve assembly that arecommon with those of FIG. 1 are provided with the same reference numbersas FIG. 1 and are not described again. The main feature of the valveassembly 102 in accordance with the invention is that the central seats18′ 20′ and land 24 of FIG. 1 have been withdrawn and replaced by avalve seat assembly in another manner so as to provide significantbenefits in terms of reducing the length of the valve assembly.

In accordance with the invention, the seats 104, 106 are no longerseparated by a land and are positioned adjacent to each other as shownin detail in FIG. 4. In addition, the seats are now acted upon bybiasing means in the form of springs 108 which are common to both seatsinasmuch that the ends 110 of the springs are positioned act on the seat104 to apply force to move the seat towards the ball 16 of valve unit 12and the ends 114 of the springs act on the seat 106 to move the sametowards the ball 16 of valve unit 14.

It will be appreciated that the springs can be spaced around the seatsso as to allow a uniform force to be exerted thereon. Also the pressureof the fluid acts in conjunction with the springs to move the seattowards the ball and typically, dependent on the direction of fluidthrough the passage 6 of the valve assembly, at any given time thesprings will be exerting a greater force in one direction on one seatthan on the other seat. Typically the biasing means will be exerting agreater force on the valve seat 104 or 106 which is positioneddownstream with respect to the direction of flow of fluid along thevalve passage.

The valve body can be formed of two parts joined together at aninterface which is located intermediate the valves 12,14 as shown inFIG. 3, or alternatively can be a single part in which the componentsare introduced from one end and a bolt on end flange is provided tocomplete the assembly as shown in FIG. 2. Alternatively a singlethreaded insert can be used.

The present invention therefore allows the characteristics of operationof the valve assembly of this type to be maintained and also allows thelength of the valve assembly to be reduced, which has considerablebenefit.

1. A valve assembly, said valve assembly including a valve body housing,first and second valve balls, and between said first and second valveballs are provided first and second valve seats wherein common biasingmeans are provided which are capable of biasing said valve seats towardstheir respective valve balls.
 2. An assembly according to claim 1wherein the biasing means is a spring.
 3. An assembly according to claim2 wherein the spring is a coil spring, wave spring and/or disc spring.4. An assembly according to claim 1 wherein the biasing means arepositioned to lie between the said first and second seats, with a firstend of the biasing means acting on the first valve seat and the opposingend of the said biasing means acting on the second valve seat.
 5. Anassembly according to claim 1 wherein when the fluid flows through thevalve in a first direction, the biasing means acts on one of the firstor second seats to move the same towards the first or second valve ballrespectively and, when the fluid flows through the valve in the opposingdirection, the same biasing means acts on the other of the first orsecond seats to move that seat towards the other of the first or secondballs.
 6. An assembly according to claim 5 wherein the valve seat actedon by the biasing means is that which is located downstream with respectto the direction of the flow of fluid through the valve passage.
 7. Anassembly according to claim 1 wherein the first and second seats andbiasing means are provided as a seat assembly located within a valveassembly.
 8. An assembly according to claim 1 wherein the valve seatsare provided to seal against the valve ball.
 9. An assembly according toclaim 1 wherein a single biasing means is provided.
 10. An assemblyaccording to claim 1 wherein a plurality of biasing means are provided,each capable of acting on the said first and second seats.
 11. Anassembly according to claim 1 wherein the fluid acts in conjunction withbiasing means to exert a movement force on said first or second seatdepending on the direction of flow of the fluid.
 12. An assembly whereinthe valve body is formed from two parts and the interface between whichis located at or adjacent to the location of the first and second valveseats and biasing means therefore.
 13. An assembly according to claim 1wherein the valve body is formed as one part and the seats and biasingmeans are introduced into position from an end of the valve body.
 14. Anassembly according to claim 1 wherein the valve body is provided in twoparts which are joined together intermediate the ends of the valve body.15. An assembly according to claim 14 wherein the join is locatedsubstantially centrally with respect to the length of the valve body.16. An assembly according to claim 1 wherein the valve includes apassage which passes from a first end to a second end of the valve body,said valves balls provided spaced along the passage and each valve ballis provided to allow the selective closing and opening of the passage.17. An assembly according to claim 16 wherein a vent is locatedintermediate the first and second valve balls.
 18. An assembly accordingto claim 17 wherein the vent is formed around the circumference of theseat assembly.
 19. An assembly according to any of the preceding claims1 wherein the overall length of the valve assembly is at or less thanthe required ANSI B16:10 length for the particular pipe diameter towhich the valve is to be fitted.
 20. A double block and bleed valveassembly, said assembly including a first ball valve unit and a secondball valve unit spaced apart in a fluid passage through the valveassembly and wherein, intermediate said first and second ball valvesthere is provided a seat assembly including a first seat and a secondseat and biasing means capable of exerting a biasing force on the firstand second seats in opposing directions.
 21. An assembly according toclaim 20 wherein the same biasing means exert a biasing force on boththe first and second seats and are retained in position between thesame.
 22. An assembly according to claim 20 wherein the biasing force isused to move the seats to seal on the ball of the respective first andsecond valves.
 23. An assembly according to claim 20 wherein the biasingmeans are spaced around the circumference of the seats so as to exert auniform movement force around each of the seats.
 24. An assemblyaccording to claim 20 wherein at any given time, the biasing means exerta biasing force to move one of the seats onto the adjacent wall with theparticular seat in question being that which lies downstream of thebiasing means with respect to the flow of fluid through the valveassembly at that time.